The invention relates to the field of heat exchangers and, more particularly, the heat exchangers used in the motor vehicle domain.
A heat engine of a motor vehicle comprises a combustion chamber, generally formed by a plurality of cylinders, in which a mixture of oxidant and fuel is burned to generate the work of the engine. The gases taken into the combustion chamber are called intake gases.
In some cases, these intake gases have to be cooled before being introduced into the combustion chamber; this function is fulfilled by a heat exchanger, which is a cooler.
Conventionally, a heat exchanger comprises a heat exchange bundle formed by a plurality of exchange elements stacked between two end plates (bottom plate and top plate). The spaces between the exchange elements of the bundle form ducts for a flow of gas to be cooled, here intake gases. The exchange elements of the bundle are hollow and conduct a heat transfer fluid, intended to exchange heat with the flow of gas to be cooled circulating in the fluid ducts and thus cool it.
In order to reduce the polluting emissions, it is known practice to introduce, into the flow of intake gas, so-called “recirculated” exhaust gases. These are exhaust gases taken downstream of the combustion chamber in order to be rerouted (recirculated) to the flow of intake gas, upstream of the combustion chamber, where they are mixed with the intake gases prior to their intake into the combustion chamber. Traditionally, the recirculated exhaust gases are introduced via one or more introduction points formed in an intake duct for the gases extending between the cooler of the intake gases and the engine, in order for the recirculated exhaust gases to be mixed with the gases originating from the cooler.
A current trend aims to bring the heat exchanger as close as possible to the engine in order to gain in compactness.
The patent application published under the number WO2008/116568 teaches a heat exchange module intended to be mounted on the cylinders of an internal combustion engine. With reference to FIGS. 1 and 2 representing the module of the application WO2008/116568, the heat exchange module comprises, in its upstream part 110, a heat exchange bundle 111, and in its downstream part 103, output ducts 106 arranged to be connected respectively to the cylinders of the engine.
During its operation, a flow of intake gas G is introduced via an upstream face of the exchange module to be cooled by the heat exchange bundle 111, the cooled flow then being distributed in the output ducts of the exchange module to be taken into the cylinders of the engine to which the ducts 106 are respectively connected.
Each output duct 106 of the heat exchange module, in which the flow of cooled intake gas G circulates, comprises an injection orifice 107 for a flow of recirculated exhaust gases H, which is injected by an injection duct 105 connected to the output duct 106 of the exchange module at the level of said injection orifice 107, as represented in FIG. 2. Thus, the flow of intake gas G and the flow of recirculated exhaust gases H are mixed in the output ducts 106 of the module before their intake into the cylinders of the engine.
As represented in FIG. 2, the recirculated exhaust gases are injected in a direction orthogonal to the direction of the flow of intake gas which requires the injection ducts 105 to be added onto the exchange module which increases its volume.
Moreover, in order to allow for a uniform mixing between the two gas flows, it is necessary for the mixing module to have a sufficient length downstream of the place of injection. For a compact exchange module, an injection of the flow of exhaust gas orthogonally to the flow of intake gas makes it difficult to create sufficient entropy for the homogenization of the mixture.